The goal of vegetable breeding is to combine various desirable traits in a single variety/hybrid. Such desirable traits may include any trait deemed beneficial by a grower and/or consumer, including greater yield, resistance to insects or disease, tolerance to environmental stress, and nutritional value.
Breeding techniques take advantage of a plant's method of pollination. There are two general methods of pollination: a plant self-pollinates if pollen from one flower is transferred to the same or another flower of the same plant or plant variety. A plant cross-pollinates if pollen comes to it from a flower of a different plant variety.
Plants that have been self-pollinated and selected for type over many generations become homozygous at almost all gene loci and produce a uniform population of true breeding progeny, a homozygous plant. A cross between two such homozygous plants of different genotypes produces a uniform population of hybrid plants that are heterozygous for many gene loci. Conversely, a cross of two plants each heterozygous at a number of loci produces a population of hybrid plants that differ genetically and are not uniform. The resulting non-uniformity makes performance unpredictable.
The development of uniform varieties requires the development of homozygous inbred plants, the crossing of these inbred plants, and the evaluation of the crosses. Pedigree breeding and recurrent selection are examples of breeding methods that have been used to develop inbred plants from breeding populations. Those breeding methods combine the genetic backgrounds from two or more plants or various other broad-based sources into breeding pools from which new lines and hybrids derived therefrom are developed by selfing and selection of desired phenotypes. The new lines and hybrids are evaluated to determine which of those have commercial potential.
One crop species which has been subject to such breeding programs and is of particular value is squash. The term squash is used to refer to four species of the genus Cucurbita of the family Cucurbitaceae: (1) C. maxima, which includes the Hubbard, buttercup, and some large pumpkins, (2) C. mixta, including cushaw squash, (3) C. moschata, which includes the butternut squash, and (4) C. pepo. Acorn squash, zucchini, yellow crookneck and straightneck, and most pumpkins belong to this last species.
The term squash encompasses pumpkins, marrows, and zucchinis. Exclusively ornamental and functional varieties are included among gourds. There is considerable variation in size, shape and color. A typical categorization is to distinguish between summer and winter varieties. Summer squashes include young vegetable marrows, such as zucchini, and are harvested during the summer months. At this stage, the skin of the fruit is tender and the fruit relatively small. Common fruit forms include straightneck, crookneck, saucer shaped, and oblong.
While breeding efforts to date have provided a number of useful squash lines with beneficial traits, there remains a great need in the art for new lines with further improved traits. Such plants would benefit farmers and consumers alike by improving crop yields and/or quality.